The present invention relates to new high performance polymer and copolymer compositions for extended-life coating applications.
Coating primer requirements for advanced coating technology have become more stringent than those provided by the-state-of-the-art materials. Commercial materials utilized for primers generally last between 3 and 7 years. The removal of such primers involves high cost with respect to both materials and labor. Failure of these materials is primarily due to delamination (adhesive failure), and acid rain. The labor costs of applying and removing failed primers is considerable; accordingly, new coating materials are required that are acid stable and have extended-life times of 30+ years of service.
We have synthesized new acid stable material compositions based on benzazole homo- and co-polymer systems, tailored with allyl pendent groups for maximizing processability and properties. Benzazole polymers are very acid stable since they are prepared in polyphosporic acid (PPA) at about 180xc2x0 C. The introduction of pyrazole groups along the backbone of the benzazole polymer allows post-polymer reactions to incorporate allyl pendent groups utilized for free radical crosslinking reactions.
Accordingly, it is an object of the present invention to provide new crosslinkable material compositions based on benzazole homo- and co-polymer systems.
Other objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
In accordance with the present invention there is provided a new benzazole polymers/copolymer system. This new polymer system has repeating units of the formula: 
wherein Bz is a benzazole unit selected from the group consisting of 
wherein X is xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94or xe2x80x94NHxe2x80x94, and R is selected from the group consisting of 
wherein Ar is an aromatic group; and wherein x has a value of about 1.0 to 0.1 and y has a value of 1.0xe2x88x92x.
The polymers and copolymers of this invention are derived from 1-H-pyrazole-3,5-dicarboxcylic acid. The incorporated pyrazole repeat unit allows for post-polymer reactions to provide allyl pendent groups which can be utilized to cure or crosslink the polymer/copolymer units.
The homopolymers are prepared by the condensation of approximately equimolar amounts of 1-H-pyrazole-3,5-dicarboxcylic acid (PDC) and a benzazole precursor such as 
wherein R and X are as defined previously, in polyphosporic acid (PPA) at about 180xc2x0 C., following procedures well known in the art, then recovered, also using procedures well known in the art.
The copolymers are prepared in similar manner by the condensation of approximately equimolar amounts of (a) a mixture of 1-H-pyrazole-3,5-dicarboxcylic acid (PDC) and an aromatic dicarboxylic acid, and (b) a benzazole precursor as defined above.
The pyrazole-containing homo- and copolymer compositions are then derivatized utilizing the pyrazole proton. Derivatization of these compositions is carried out by treatment with sodium hydride in anhydrous DMSO to form dark red viscous polyanions. One equivalent of sodium hydride is used per pyrazole repeat unit. After complete dissolution of the polyanion, excess allylbromide is added and the mixture heated to about 40-60xc2x0 C. The resulting derivatized polymer/copolymer is recovered by precipitation into water, followed by soxhlet extraction with heptane to remove unreacted allylbromide. The pendent allyl polymer/copolymer can be crosslinked using the appropriate free radical-initiating reagents.